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The U.S. Steel Edgar Thomson Emissions Consent Decree Explained

Updated: Feb 2, 2023

As GASP reported Monday, like it or not, U.S. Steel’s Edgar Thomson facility is now subject to the terms of a court-approved consent decree entered into by the company, the Allegheny County Health Department (ACHD), the Department of Justice (DOJ), and the Environmental Protection Agency (EPA).

The goals of the consent decree are to resolve various issues at Edgar Thomson that led to a joint enforcement action between EPA and ACHD against U.S. Steel in 2017 and ensure the facility complies with applicable air quality laws and regulations going forward.

The decree itself spells out a series of measures U.S. Steel must take to meet those goals. GASP staff reviewed the final agreement and put together a summary of what it requires in plain English:

Pig Iron, Casting Slabs, and the BOP Shop

(a quick rundown of the terminology you’ll need to understand first)

U.S. Steel’s Mon Valley Works is what is known as an integrated steelmaking operation. That means U.S. Steel starts with raw materials – iron ore, coal, etc. – and produces finished steel.

The Edgar Thomson facility makes molten iron (or pig iron) in its blast furnaces using coke from Clairton, iron ore, and other materials. Within the blast furnace casthouses, the furnaces are tapped and the pig iron is collected in rail cars (called torpedo cars) for transfer. A molten sulfurous metallic waste product of the blast furnace is slag, which is diverted into open pits to cool before processing.

The facility turns iron into steel by way of the basic oxygen process (BOP) in a part of the mill aptly named the BOP shop. Molten steel is poured into a continuous caster that creates steel slabs, which are then shipped by rail to the Irvin Works for finishing.

We created a guide to the blast furnace and BOP shop locations with labeled photos you can view here.

Consent Decree Terms

Actions U.S. Steel must take fall into three broad categories: emissions reductions from specific processes, enhanced emissions monitoring, and enhanced equipment maintenance.


The most immediate action required is that by Feb. 14, U.S. Steel must begin “feeding an oxidizing chemical additive or additives . . . into the slag pit quench water spray system, to enhance suppression of H2S emissions.”

Within 90 days of starting that process – but by May 15 at the latest – the company is required to submit to the EPA and ACHD written procedures detailing how it will continue to reduce emissions from slag pit operations.

U.S. Steel must also reduce emissions from the blast furnaces’ casthouse baghouse system, the BOP shop roof ventilation, and the BOP shop scrubber system. Unfortunately, these improvements won’t be in place anytime soon: U.S. Steel must first obtain independent engineering evaluations to identify potential emissions reduction improvements.

The consent decree states, “U. S. Steel has retained and EPA, after consultation with ACHD, has approved” independent third-party contractors to conduct studies of all three systems. For all three studies, the contractors must submit detailed plans for conducting the studies that ACHD and EPA must then approve outright, approve with conditions, approve partially, or reject.

Here is what the consent decree says about the timeline:

  • The plan for the casthouse study was due Jan 15. The plans for the two BOP shop studies are due Feb 14.

  • The studies must be completed within 120 days after they are approved, but when the approvals will be issued is anyone’s guess (there are no approval deadlines in the consent decree).

  • U.S. Steel must submit copies of the final studies to EPA and ACHD within 90 days of their completion, along with a report that details improvements recommended by the third-party contractor and reasons why they should or should not be considered, cost estimates for proposed projects, and a schedule to complete the projects.

  • Once again, after approval (however long that takes), U.S. Steel “shall implement the proposed actions” laid out in the schedule.

  • Finally, U.S. Steel must submit to EPA and ACHD a notice of completion certifying that the actions were implemented in accordance with the approved plans.

Given the unknown approval turnaround times, we can’t say for sure when these improvements will be in place. So far, ACHD has declined the invitation – via the public comment period – to establish a website where these documents could be posted and deadlines updated.

Via public records requests, GASP hopes to update the public as work progresses.


By June 14, U.S. Steel must permanently install and maintain no fewer than seven video cameras aimed at problematic sources of visible emissions including the blast furnace stove stacks, casthouse roof monitors and baghouse, BOP shop roof monitor and scrubber stacks, and two staging areas for torpedo cars.

These cameras will not be a way for regulators to determine compliance with air quality regulations. Rather, the decree states they will be used to keep a better eye on potential emissions sources so U.S. Steel can take “corrective actions to minimize or eliminate any such emissions as expeditiously as possible.”

In addition to the camera system, by Jan. 15, U.S. Steel was to have ensured a third-party observer – trained and certified in accordance with EPA Method 9 – began conducting visible emissions readings covering the casthouse roof monitors, BOP shop roof monitor, and BOP shop scrubber stacks twice a week when the equipment was operating.

You might recognize that the areas subject to Method 9 scrutiny are also the three areas with pending engineering studies (see above). That is intentional – this will help the EPA and ACHD be certain the upgrades measurably reduce emissions.

In fact, within 30 days after U. S. Steel submits the notices of completion for the upgrades required in those studies, the Method 9 inspection frequency will increase to four days per week. This extra monitoring will end after four consecutive months of 100 percent compliance or 12 months from the start of the more frequent inspections (whichever is sooner).

Both before and after the upgrades, the agreement requires U.S. Steel to provide information weekly on when and where the visible emissions readings will be taken to allow an ACHD staff member or contractor the opportunity to be present during the readings “and, as necessary, perform ACHD’s own observations to verify compliance.”

U.S. Steel must generate a report for each Method 9 reading required by the decree and submit quarterly reports of its compiled Method 9 observations. These reports must identify any deviation(s) from the applicable opacity standards as well as the “likely cause of such deviations(s), corrective measure(s) taken to address the deviation(s), and the effectiveness of such corrective measures as can be determined at the time of the report.”

Finally, by March 16, U.S. Steel must submit a monitoring plan to install a continuous SO2 monitor for the facility’s riley boilers. These boilers burn blast furnace gas, coke oven gas, and natural gas to generate steam, heat, and electricity for the plant.


A third-party auditor will conduct a maintenance practices audit that will analyze emissions control operations and maintenance practices for the casthouse baghouse, the BOP shop fugitive emissions baghouse, the BOP shop mixer baghouse, the BOP shop LMF baghouse, the BOP shop primary emissions system/BOP shop scrubber, and the slag pits.

The auditor will have access to all records, employees, contractors, and areas of the facility deemed reasonably necessary to effectively conduct the audit.

By June 14, the auditor must submit a report to U.S. Steel that includes:

  • a summary of the audit process, including any obstacles encountered

  • detailed audit findings, including the basis for each finding and each area of concern related to the adequacy of Edgar Thomson’s operations and maintenance plan for ensuring current and continued future functioning of emissions controls and compliance with applicable emission limitations

  • information about whether requirements, targets, objectives, or other benchmarks are being achieved; whether there are examples of noncompliance with the operations and maintenance plan; and “recommendations for resolving areas of concern or otherwise achieving compliance with the operations and maintenance”

  • A certification by the third-party contractor and U. S. Steel that the audit was performed in accordance with the proposed consent decree.

Within 60 days of receiving the auditor’s report, U.S. Steel must submit that report to the EPA and ACHD along with a proposal for implementing any recommendations in the report.

In addition to the third-party audit, U.S. Steel must undergo self-audits every 12 months and submit for approval plans to EPA and ACHD detailing everything from obstacles encountered to the adequacy of the operations and maintenance plan to whether required objectives and benchmarks are being met.


The consent decree requires U.S. Steel to submit to EPA and ACHD semi-annual reports detailing everything from the progress made on required upgrades and training to problems encountered and changes made to the facility’s operations or maintenance plans.

Those reports must be submitted by Feb. 28 and Aug. 31 each year.

Editor’s Note: GASP staff is following the consent decree issue - and deadlines therein - carefully and will keep you posted.

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